The present invention relates to a serial printer having a petal-type print thimble, and more particularly to an improved carrier unit in a serial printer which selects and prints one of the characters arranged on one of the upper and lower positions on the peripheral surface of a print thimble.
A conventional carrier unit for a serial printer of this type is equipped with a petal-type print thimble which has a plurality of characters on the surface thereof, as disclosed in U.S. patent application Ser. No. 477,833. In order to select one of these characters, the print thimble is rotated in a horizontal direction and is also shifted in a vertical direction. The petal-type print thimble is secured to an upper portion of the axle of a first stepping motor and is rotated with the axle in the horizontal direction. The rotary axle of the first stepping motor can also be shifted in the vertical direction. An eccentric cam engages a lower portion of the rotary axle of the first stepping motor. In order to rotate the eccentric cam, a second stepping motor is provided underneath the first stepping motor. The rotary axle of the second stepping motor is disposed perpendicularly to that of the first stepping motor.
Namely, a first stepping motor for rotating the petal-type print thimble in the horizontal direction, and a second stepping motor for shifting the print thimble in the vertical direction are respectively required in order to select characters. Further, the carrier unit requires still another motor for driving the inked ribbon disposed between the print thimble and the printing paper.
In the conventional carrier unit for the serial printer, as mentioned above, separate drive motors are required to perform respective operations with the result that the manufacturing cost of the printer increases.